Automotive air conditioning systems are provided in most vehicles to cool the passenger compartment of the vehicle during hot weather. In general, automotive air conditioning systems comprise a compressor coupled to the engine that compresses a refrigerant to its liquid state. The compressed liquid refrigerant is then delivered to a heat exchanger within the duct work of the air conditioning system, where it is allowed to expand and cool the exchanger. A blower forces air across the heat exchanger and into the passenger compartment of the vehicle. As the air passes through the cold heat exchanger, it is cooled and the latent heat that was contained in the air is transferred to the refrigerant within the heat exchanger. Thus, the passenger compartment receives cool air. The heated refrigerant is then passed through a radiator where it is cooled and then delivered back to the compressor where the cycle begins anew.
As warm air passes through the heat exchanger of an automotive air conditioning system to be cooled, water vapor contained in the warm air condenses on the surfaces of the heat exchanger. During normal operation of the vehicle, the water vapor that condenses on the heat exchanger simple runs to the bottom of the exchanger and is drained from the air conditioning system onto the roadway. However, when the vehicle's engine is shut off and the air conditioner is no longer in operation, the water that has condensed on the heat exchanger begins to evaporate within the duct work of the air conditioning system and, as a result, a damp dank atmosphere is created. Such an atmosphere is ideal for the growth of mold, mildew, and other fungus and bacteria within the duct work of the system and particularly on the moist and wet surfaces of the heat exchanger. The growth of such organisms, in turn, results in a stale and unpleasant odor within the passenger compartment itself and can lead to airborne spores and other organisms that are unhealthy for the occupants of the vehicle.
In the past, there have been attempts to address the problems of fungus and bacteria buildup within automotive air conditioning systems. U.S. Pat. No. 5,385,028 of Gavlak, for example, discloses a method of eliminating odor in a heat pump system of a vehicle. The Gavlak method comprises determining when operation of the vehicle has been discontinued by sensing the removal of the ignition key from the ignition switch and by sensing the release of pressure from the seats of the vehicle indicating that passengers have disembarked. When these two criteria have been met, a reversing valve is activated to reverse the flow of refrigerant through the heat pump system of the vehicle in a direction opposite to the direction in which it had been flowing. As the refrigerant flows in the reverse direction, the blower of the system is activated to blow moisture off of internal surfaces of the system. The reversing of refrigerant flow tends to heat the heat exchanger, thereby accelerating the evaporation of moisture therefrom, whereupon blower operation tends to remove the moisture from the system.
While the method and apparatus of Gavlak may function adequately to dry a vehicle air conditioning system, it is nevertheless plagued with a variety of problems and shortcomings inherent in its design. One of the main problems with the Gavlak solution resides in its complexity. For example, in order to operate, the Gavlak device must be coupled to the ignition switch of the vehicle in such a way that removal of the ignition key can be detected. Furthermore, Gavlak requires that pressure sensors be installed in the seats of the vehicle in order to determine when passengers have disembarked from the vehicle. In addition, the device of Gavlak must be coupled to a reversing valve in order to reverse the coolant through the heat pump system of the vehicle and must also be coupled to the blower of the system so that the blower can be operated under the appropriate circumstances.
The complexity of Gavlak is particularly troublesome in cases where the device of Gavlak is to be retrofitted onto vehicles that were not provided from the factory with such functions. In these instances, proper installation of the Gavlak device is so complex that many average mechanics are unable to complete the installation and specially trained mechanics who usually work directly for automotive companies are required. Because of such labor costs and because of the complexity of the Gavlak device including its various sensors and switches, the Gavlak method is expensive to implement such that most vehicle owners will not afford to have the device installed.
General Motors also provides an air conditioner delay blower control module that can be installed as a retrofit on GM vehicles. However, this device, like that disclosed in Gavlak, is extremely complex and requires electrical connection to no less than seven or eight components of the vehicle's electrical and air conditioning systems. Thus, for the same reasons discussed above, the preexisting General Motors device is also prohibitively complex and expensive.
Accordingly, there exists a continuing and heretofore unaddressed need for a reliable method of eliminating the growth of fungus such as mold, mildew, and other organisms within a vehicle's air conditioning system to eliminate the odor and other undesirable consequences thereof. Such a method and apparatus should be relatively inexpensive so that it is affordable as a retrofit on existing vehicles, should operate reliably and conveniently for many years, and should be extremely simple to install so that even the most modest auto mechanic can provide installation services. It is to the provision of such a method and apparatus that the present invention is primarily directed.